Biocompatible tubing for liquid chromatography systems

ABSTRACT

A biocompatible tube that can be used in a liquid chromatography system is described. The tube can have flanged or straight ends, and can be used in conjunction with one or more fitting, assembly.

CROSS-REFERENCE FOR RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/372.427, filed Aug. 10, 2010, and U.S.Provisional Patent Application Ser. No. 61/474,653, filed Apr. 12, 2011,and is a continuation-in-part of U.S. patent application Ser. No.12/838,032, filed Jul. 16, 2010, each of which are incorporated hereinby reference in their entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to tubing for use in connectingcomponents of liquid chromatography and other analytical systems, andrelates more particularly to tubing that is coated or lined with abiocompatible polymer for use in connecting components in liquidchromatography systems used in ultra-high pressure liquidchromatography.

2. Description of the Related Art

Liquid chromatography (LC) is a well-known technique for separating theconstituent elements in a given sample. In a conventional LC system, aliquid solvent (referred to as the “mobile phase”) is introduced from areservoir and is pumped through the LC system. The mobile phase exitsthe pump under pressure. The mobile phase then travels via tubing to asample injection valve. As the name suggests, the sample injection valveallows an operator to inject a sample into the LC system, where thesample will be carried along with the mobile phase.

In a conventional LC system, the sample and mobile phase pass throughone or more filters and often a guard column before coming to thecolumn. A typical column usually consists of a piece of steel tubingwhich has been packed with a “packing” material. The “packing” consistsof the particulate material “packed” inside the column. It usuallyconsists of silica- or polymer-based particles, which are oftenchemically bonded with a chemical functionality. The packing material isalso known as the stationary phase. One of the fundamental principles ofseparation is the mobile phase continuously passing through thestationary phase. When the sample is carried through the column (alongwith the mobile phase), the various components (solutes) in the samplemigrate through the packing within the column at different rates (i.e.,there is differential migration of the solutes). In other words, thevarious components in a sample will move through the column at differentrates. Because of the different rates of movement, the componentsgradually separate as they move through the column. Differentialmigration is affected by factors such as the composition of the mobilephase, the composition of the stationary phase (i.e., the material withwhich the column is “packed”), and the temperature at which theseparation takes place. Thus, such factors will influence the separationof the sample's various components.

Once the sample (with its components now separated) leaves the column,it flows with the mobile phase past a detector. The detector detects thepresence of specific molecules or compounds. Two general types ofdetectors are used in LC applications. One type measures a change insome overall physical property of the mobile phase and the sample (suchas their refractive index). The other type measures only some propertyof the sample (such as the absorption of ultraviolet radiation). Inessence, a typical detector in a LC system can measure and provide anoutput in terms of mass per unit of volume (such as grams permilliliter) or mass per unit of time (such as grams per second) of thesample's components. From such an output signal, a “chromatogram” can beprovided; the chromatogram can then be used by an operator to determinethe chemical components present in the sample.

In addition to the above components, a LC system will often includefilters, check valves, a guard column, or the like in order to preventcontamination of the sample or damage to the LC system. For example, aninlet solvent filter may be used to filter out particles from thesolvent (or mobile phase) before it reaches the pump. A guard column isoften placed before the analytical or preparative column; i.e., theprimary column. The purpose of such a guard column is to “guard” theprimary column by absorbing unwanted sample components that mightotherwise bind irreversibly to the analytical or preparative column.

In practice, various components in an LC system may be connected by anoperator to perform a given task. For example, an operator will selectan appropriate mobile phase and column, then connect a supply of theselected mobile phase and a selected column to the LC system beforeoperation. In order to be suitable for high performance liquidchromatography (HPLC) applications, each connection must be able towithstand the typical operating pressures of the HPLC system. If theconnection is too weak, it may leak. Because the types of solvents thatare sometimes used as the mobile phase are often toxic and because it isoften expensive to obtain and/or prepare many samples for use, any suchconnection failure is a serious concern.

It is fairly common for an operator to disconnect a column (or othercomponent) from a LC system and then connect a different column (orother component) in its place after one test has finished and before thenext begins. Given the importance of leak-proof connections, especiallyin HPLC applications, the operator must take time to be sure theconnection is sufficient. Replacing a column (or other component) mayoccur several times in a day. Moreover, the time involved indisconnecting and then connecting a column (or other component) isunproductive because the LC system is not in use and the operator isengaged in plumbing the system instead of preparing samples or othermore productive activities. Hence, the replacement of a column in aconventional LC system involves a great deal of wasted time andinefficiencies.

Given concerns about the need for leak-free connections, conventionalconnections have been made with stainless steel tubing and stainlesssteel end fittings. More recently, however, it has been realized thatthe use of stainless steel components in a LC system have potentialdrawbacks in situations involving biological samples. For example, thecomponents in a sample may attach themselves to the wall of stainlesssteel tubing. This presents problems because the detector's measurements(and thus the chromatogram) of a given sample may not accurately reflectthe sample if some of the sample's components or ions remain in thetubing, and do not pass the detector. Perhaps of even greater concern,however, is the fact that ions from the stainless steel tubing maydetach from the tubing and flow past the detector, thus leading topotentially erroneous results. Additionally, ions can easily bind tobiological compounds of interest, resulting in changes to the moleculesthat affect their retention time in the column. Hence, there is a needfor “biocompatible” connections through the use of a material that ischemically inert with respect to such “biological” samples and themobile phase used with such samples so that ions will not be released bythe tubing and thus contaminate the sample.

In many applications using selector/injector valves to direct fluidflows, and in particular in liquid and gas chromatography, the volume offluids is small. This is particularly true when liquid or gaschromatography is being used as an analytical method as opposed to apreparative method. Such methods often use capillary columns and aregenerally referred to as capillary chromatography. In capillarychromatography, both gas phase and liquid phase, it is often desired tominimize the internal volume of the selector or injector valve. Onereason for this is that a valve having a large volume will contain arelatively large volume of liquid, and when a sample is injected intothe valve the sample will be diluted, decreasing the resolution andsensitivity of the analytical method.

Micro-fluidic analytical processes also involve small sample sizes. Asused herein, sample volumes considered to involve micro-fluidictechniques can range from as low as volumes of only several picolitersor so, up to volumes of several milliliters or so, whereas moretraditional LC techniques, for example, historically often involvedsamples of about one microliter to about 100 milliliters in volume.Thus, the micro-fluidic techniques described herein involve volumes oneor more orders of magnitude smaller in size than traditional LCtechniques. Micro-fluidic techniques can also be expressed as thoseinvolving fluid flow rates of about 0.5 ml/minute or less.

Most conventional HPLC systems include pumps which can generaterelatively high pressures of up to around 5,000 psi to 6,000 psi or so.In many situations, an operator can obtain successful results byoperating a LC system at “low” pressures of anywhere from just a few psior so up to 1,000 psi or so. More often than not, however, an operatorwill find it desirable to operate a LC system at relatively “higher”pressures of over 1,000 psi.

Another, relatively newer liquid chromatography form is Ultra HighPerformance Liquid Chromatography (UHPLC) in which system pressureextends upward to about 1400 bar or 20,000 psi or so, or even more. Inorder to achieve greater chromatographic resolution and higher samplethroughput, the particle size of the stationary phase has becomeextremely small. A stationary phase particle as small as 1 micron iscommon; the resulting high column packing density leads to substantiallyincreased system pressure at the head of the column. Both HPLC and UHPLCare examples of analytical instrumentation that utilize fluid transferat elevated pressures. For example, in U.S. Patent Publication No. US2007/0283746 A1, published on Dec. 13, 2007 and titled “Sample InjectorSystem for Liquid Chromatography,” an injection system is described foruse with UHPLC applications, which are said to involve pressures in therange from 20,000 psi to 120,000 psi. In U.S. Pat. No. 7,311,502, issuedon Dec. 25, 2007 to Gerhardt, et al., and titled “Method for Using aHydraulic Amplifier Pump in Ultrahigh Pressure Liquid Chromatography,”the use of a hydraulic amplifier is described for use in UHPLC systemsinvolving pressures in excess of 25,000 psi. In U.S. Patent PublicationNo. US 2005/0269264 A1, published on Dec. 8, 2005 and titled“Chromatography System with Gradient Storage and Method for Operatingthe Same,” a system for performing UHPLC is disclosed, with UHPLCdescribed as involving pressures above 5,000 psi (and up to 60,000 psi).Applicants hereby incorporate by reference as if fully set forth hereinU.S. Pat. No. 7,311,502 and US Patent Publications Nos. US 2007/0283746A1 and US 2005/0269264 A1.

As noted, liquid chromatography (as well as other analytical) systems,including HPLC or UHPLC systems, typically include several components.For example, such a system may include a pump; an injection valve orautosampler for injecting the analyte; a precolumn filter to removeparticulate matter in the analyte solution that might clog the column; apacked bed to retain irreversibly adsorbed chemical material; the HPLCcolumn itself; and a detector that analyzes the carrier fluid as itleaves the column. These various components may typically be connectedby a miniature fluid conduit, or tubing, such as metallic or polymerictubing, usually having an internal diameter of 0.001 to 0.040 inch.

All of these various components and lengths of tubing are typicallyinterconnected by threaded fittings. Fittings for connecting various LCsystem components and lengths of tubing are disclosed in prior patents,for example, U.S. Pat. Nos. 5,525,303; 5,730,943; and 6,095,572, thedisclosures of which are herein all incorporated by reference as iffully set forth herein. Often, a first internally threaded fitting sealsto a first component with a ferrule or similar sealing device. The firstfitting is threadedly connected through multiple turns by hand or by useof a wrench or wrenches to a second fitting having a correspondingexternal fitting, which is in turn sealed to a second component by aferrule or other seal. Disconnecting these fittings for componentreplacement, maintenance, or reconfiguration often requires the use of awrench or wrenches to unthread the fittings. Although a wrench orwrenches may be used, other tools such as pliers or other gripping andholding tools are sometimes used. It will be understood by those skilledin the art that, as used herein, the term “LC system” is intended in itsbroad sense to include all apparatus and components in a system used inconnection with liquid chromatography, whether made of only a few simplecomponents or made of numerous, sophisticated components which arecomputer controlled or the like. Those skilled in the art will alsoappreciate that an LC system is one type of an analytical instrument(AI) system. For example, gas chromatography is similar in many respectsto liquid chromatography, but obviously involves a gas sample to beanalyzed. Such analytical instrument systems include high performance orhigh pressure liquid chromatography systems, an ultra high performanceor ultra high pressure liquid chromatography system, a mass spectrometrysystem, a microflow chromatography system, a nanoflow chromatographysystem, a nano-scale chromatography system, a capillary electrophoresissystem, a reverse-phase gradient chromatography system, or a combinationthereof. Although the following discussion focuses on liquidchromatography, those skilled in the art will appreciate that much ofwhat is said also has application to other types of AI systems andmethods.

Increasing pressure requirements in liquid chromatography havenecessitated the use of high pressure fluidic components. For manyapplications regular stainless steel tubing can be used to withstand thehigh pressure. However, for some types of analyses (e.g., biologicaltesting and metal/ion analysis), stainless steel or other metals are notdesired in the fluid path as the metal could interfere with the testing.Additionally, there are some fields of use (e.g., nano-scale ornano-volume analysis), that require very small inside diameters toaccommodate the extremely low volumes required by these applications.Such small inside diameters are typically not available in stainlesssteel or other high pressure tubing.

Therefore, it is an object of the present invention to providebiocompatible tubing for use in an HPLC or UHPLC system. An additionalobject of the present invention is to provide biocompatible tubing withvery small inside diameters that can be used in nano-scale ornano-volume applications.

The above and other advantages of the present invention will becomereadily apparent to those skilled in the art from the following detaileddescription of the present invention, and from the attached drawings,which are briefly described below.

SUMMARY OF THE INVENTION

In a first embodiment of the present disclosure, a tube is provided thatis well-suited for use in liquid chromatography systems, and isparticularly well-suited for use in high pressure liquid chromatographyand ultra high pressure liquid chromatography, and methods such as invitro diagnostics (IVD). In this embodiment, the tube comprises an outerlayer and an inner biocompatible layer defining a passageway, wherein noportion of the outer layer is in contact with the passageway, and thusno fluid is in contact with the outer layer, even at the face.

In one embodiment, the present disclosure provides a tube for use in aliquid chromatography or analytical instrument system, comprising anouter layer having an inner surface and an outer surface, and having afirst and a second end, and a biocompatible inner layer having apassageway therethrough and having a first and a second end, wherein theinner layer is located within the outer layer. In certain embodiments,portions of the first and second ends of the biocompatible inner layerextend beyond the first and second ends, respectively, of the outerlayer. In particular embodiments the outer layer is comprised of metal.In some embodiments the outer metal layer comprises stainless steel, andthe biocompatible inner layer comprises a fluoropolymer orpolyetheretherketone (PEEK).

The present disclosure further provides a tube for use in a liquidchromatography system, comprising an outer layer having an inner surfaceand an outer surface, and having a first and a second end, wherein thefirst and second ends of the outer metal layer are flanged, flared orangled, and a biocompatible inner layer having an inner surface, anouter surface, a first end, a second end and a passageway therethrough,wherein the inner layer is located within the outer layer. In certainembodiments the first and second ends of the biocompatible inner layerextend beyond the first and second ends, respectively, of the outerlayer. In particular aspects the first and second ends of the innerlayer are flanged, flared, or angled. In some embodiments the outerlayer is comprised of metal, for example stainless steel. In variousembodiments the biocompatible inner layer comprises a fluoropolymer orpolyetheretherketone (PEEK).

In certain aspects of the present disclosure, at least a portion of theinner surface of the outer layer is attached to or interacts with atleast a portion of the outer surface of the inner layer. In particularembodiments, at least 25%, at least 50%, at least 75%, at least 90%, oressentially the entire inner surface of the outer layer is attached toor interacts with the outer surface of the inner layer. In someembodiments the attachment or interaction between the outer layer andthe inner layer is friction-based. In certain embodiments the attachmentor interaction occurs through heating the tube, gluing the inner surfaceof the outer layer and the outer surface of the inner layer, crimpingthe outer layer onto the inner layer, or drawing the outer layer overthe inner layer. Thus, in certain aspects of the present disclosure theinner layer and outer layer cannot rotate independently, while in otheraspects the inner layer and the outer layer can rotate independently ofeach other.

In additional aspects of the present disclosure the tube furthercomprises at least a first fitting. In various embodiments the firstfitting is a one-piece fitting or a two-piece fitting. In otherembodiments the first fitting is removable. In further embodiments thetube further comprises at least a first and a second fitting.

The present disclosure further provides a tube for use in a liquidchromatography system, comprising an outer layer having an inner surfaceand an outer surface, and having a first and a second end, wherein atleast one of the first and second ends of the outer layer comprises atip portion and a retention feature, wherein the tip portion comprises apolymer, and a biocompatible inner layer having an inner surface, anouter surface, a first end, a second end and a passageway therethrough,wherein the inner layer is located within the outer layer. In certainembodiments the retention feature is a barb, an undercut, a groove, athread, one or more cross-drilled hole, one or more dimple, a reversetaper, a flange, or a geometric shape, including, but not limited to, asquare, a pentagon, a hexagon, a heptagon, or an octagon. In otherembodiments the first end of the outer layer comprises a first tipportion and a first retention feature, and the second end of the outerlayer comprises a second tip portion and a second retention feature,wherein the first and second tip portions comprise a polymer. In suchembodiments the first retention feature can be the same as the secondretention feature or the first retention feature can be different fromthe second retention feature.

In various embodiments the first and second ends of the biocompatibleinner layer extend beyond the first and second ends, respectively, andthe tip portion of the outer layer. In further embodiments the outerlayer is comprised of metal, for example stainless steel. In additionalembodiments the biocompatible inner layer comprises polyetheretherketone(PEEK). In other aspects tip portion comprises PEEK, for examplecarbon-fiber PEEK. In such embodiments the carbon fiber PEEK comprisesabout 10% to about 40% by weight carbon-fiber. In yet other embodimentsthe tip portion is molded onto at least one of the first and second endsof the outer layer.

In certain aspects the tube further comprises at least a first fittingassembly, while in other aspects the tube further comprises at least afirst and a second fitting assembly. In various embodiments the fittingassembly comprises a nut having a first end and a second end, and havinga passageway therethrough, wherein the passageway has an internallytapered portion and a lip proximal the second end of the nut, andwherein the second end of the nut has an externally threaded portion, aferrule having a first externally tapered end and a second end andhaving a passageway therethrough, wherein the first externally taperedend of the ferrule is adapted to securely engage with the taperedportion of the passageway in the nut, and a ferrule tip having a firstexternally tapered end, a central portion, and a second externallytapered end, wherein the first externally tapered end and the centralportion define a first lip and the second externally tapered end and thecentral portion define a second lip, and wherein the first end of theferrule tip is adapted to abut with the second end of the ferrule withinthe passageway of the nut, and the first lip of the ferrule tip securelyengages the lip of the nut. In particular embodiments the firstexternally tapered end of the ferrule comprises a plurality of members.In other embodiments the ferrule and the ferrule tip may rotateindependently. In yet other embodiments the ferrule and the ferrule tipmay actuate independently.

In certain embodiments at least a portion of an angle of the internallytapered portion of the nut and at least a portion of an angle of thefirst externally tapered end of the ferrule are between about 18° andabout 28° included angle, and the angles of the portions of theinternally tapered portion of the nut and the first externally taperedend of the ferrule differ by about 1° to about 5°. In furtherembodiments the nut, the ferrule, or the ferrule tip comprises apolymer, for example polyetheretherketone. In still further embodimentsthe polymer comprises about 10% to about 30% by weight carbon filledpolyetheretherketone. In particular aspects the nut, the ferrule, or theferrule tip comprises a metal, for example stainless steel. In someembodiments at least one of the nut, ferrule, and ferrule tip comprisespolyetheretherketone and at least one of the nut, ferrule, and ferruletip comprises stainless steel. In various embodiments the fittingassembly consists essentially of biocompatible materials.

In additional embodiments at least a portion of the passageway throughthe nut, the ferrule, or the ferrule tip is at least partially coated,while in other embodiments at least a portion of the passageway throughthe nut, the ferrule, and the ferrule tip is at least partially coated.In various embodiments at least a portion of the passageway through thenut, the ferrule, or the ferrule tip is at least partially coated with acoating comprising a nickel, silica carbide, copper or diamond coating,or a combination thereof.

The present disclosure additionally provides a tube and fitting systemfor use in a liquid chromatography system, comprising a tube comprisingan outer layer having an inner surface and an outer surface, and havinga first and a second end, wherein at least one of the first and secondends of the outer layer comprises a tip portion, wherein the tip portioncomprises a polymer, and a biocompatible inner layer having a passagewaytherethrough and having a first and a second end, wherein the innerlayer is located within the outer layer and a fitting comprising a firstferrule and a second ferrule, wherein the first ferrule comprises ametal, such as stainless steel, and the second ferrule comprises apolymer, wherein the first ferrule holds the tube by the outer layer andthe second ferrule seals the tube on the tip portion.

The present disclosure further provides a tube assembly for use in aliquid chromatography system, comprising a tube comprising an outerlayer having an inner surface and an outer surface, and having a firstand a second end, wherein at least one of the first and second ends ofthe outer layer comprises a tip portion and a retention feature, whereinthe tip portion comprises a polymer and a biocompatible inner layerhaving an inner surface, an outer surface, a first end, a second end anda passageway therethrough, wherein the inner layer is located within theouter layer, and at least a first fitting assembly associated with thefirst or second end of the outer layer. In certain aspects the retentionfeature is a barb, an undercut, a groove, a thread, one or morecross-drilled hole, one or more dimple, a reverse taper, a flange, or ageometric shape. In additional embodiments the first end of the outerlayer comprises a first tip portion and a first retention feature, andthe second end of the outer layer comprises a second tip portion and asecond retention feature, wherein the first and second tip portionscomprise a polymer. In such embodiments the first retention feature canbe the same as the second retention feature, or the first retention canbe different from the second retention feature.

In certain embodiments of the disclosed tube assembly, the fittingassembly comprises a nut having a first end and a second end, and havinga passageway therethrough, wherein the passageway has an internallytapered portion and a lip proximal the second end of the nut, andwherein the second end of the nut has an externally threaded portion, aferrule having a first externally tapered end and a second end andhaving a passageway therethrough, wherein the first externally taperedend of the ferrule is adapted to securely engage with the taperedportion of the passageway in the nut, and a ferrule tip having a firstexternally tapered end, a central portion, and a second externallytapered end, wherein the first externally tapered end and the centralportion define a first lip and the second externally tapered end and thecentral portion define a second lip, and wherein the first end of theferrule tip is adapted to abut with the second end of the ferrule withinthe passageway of the nut, and the first lip of the ferrule tip securelyengages the lip of the nut.

The present disclosure also provides an analytical instrument systemcomprising at least one tube assembly comprising a tube comprising anouter layer having an inner surface and an outer surface, and having afirst and a second end, wherein at least one of the first and secondends of the outer layer comprises a tip portion and a retention feature,wherein the tip portion comprises a polymer, and a biocompatible innerlayer having an inner surface, an outer surface, a first end, a secondend and a passageway therethrough, wherein the inner layer is locatedwithin the outer layer, and at least a first fitting assembly associatedwith the first or second end of the outer layer, the fitting assemblycomprising a nut having a first end and a second end, and having apassageway therethrough, wherein the passageway has an internallytapered portion and a lip proximal the second end of the nut, andwherein the second end of the nut has an externally threaded portion, aferrule having a first externally tapered end and a second end andhaving a passageway therethrough, wherein the first externally taperedend of the ferrule is adapted to securely engage with the taperedportion of the passageway in the nut, and a ferrule tip having a firstexternally tapered end, a central portion, and a second externallytapered end, wherein the first externally tapered end and the centralportion define a first lip and the second externally tapered end and thecentral portion define a second lip, and wherein the first end of theferrule tip is adapted to abut with the second end of the ferrule withinthe passageway of the nut, and the first lip of the ferrule tip securelyengages the lip of the nut.

In certain embodiments the analytical instrument system comprises aliquid chromatography system. In such embodiments the analyticalinstrument system comprises an ultra high pressure or ultra highperformance liquid chromatography system. In further embodiments theanalytical instrument system comprises a high performance or highpressure liquid chromatography system, an ultra high performance orultra high pressure liquid chromatography system, a mass spectrometrysystem, a microflow chromatography system, a nanoflow chromatographysystem, a nano-scale chromatography system, a capillary electrophoresissystem, a reverse-phase gradient chromatography system, or a combinationthereof.

The present disclosure additionally provides a process for preparing atube for use in a liquid chromatography system, the tube comprising abiocompatible inner layer and an outer layer, the biocompatible innerlayer and outer layer each comprising a first and a second end, and aninner surface and an outer surface, comprising treating the inner orouter layer to provide a tight fit between the inner and outer layers.In certain embodiments the process comprises cold drawing abiocompatible inner layer having a passageway therethrough and having afirst and a second end, inserting the biocompatible inner layer into anouter layer having an inner surface and an outer surface, and having afirst and a second end, and heating the inner and outer layers toprovide a tight fit between the inner and outer layers.

These and other embodiments and advantages of the disclosed tube aredescribed below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a conventional liquid chromatographysystem.

FIG. 2 is a side view of a tube with flanged, flared or angled ends inaccordance with one aspect of the present invention.

FIG. 3 is a cross-sectional side view of an end of an embodiment of thetube of FIG. 2 having flanged ends.

FIG. 4 is a cross-sectional side view of an end of an embodiment of thetube of FIG. 2 having flared ends.

FIG. 5 is a cross-sectional side view of an end of a second embodimentof the tube of FIG. 2 having angled ends.

FIG. 6 is a side view of one embodiment of one end of a tube having aflanged, flared or angled end with a fitting assembly.

FIG. 7 is a cross-sectional side view of the embodiment of an end of aflanged, flared or angled tube with a fitting assembly as shown in FIG.6.

FIG. 8 is a side view of one embodiment of a straight tube (withoutflanged ends) in accordance with one aspect of the present invention.

FIG. 9 is a cross-sectional side view of an end of an embodiment of thetube of FIG. 8.

FIG. 10 is a cross-sectional side view of an end of another embodimentof the tube of FIG. 8.

FIG. 11 is an exploded view of various components of an embodiment of afitting assembly in accordance with one aspect of the present invention.

FIG. 12 is a side view of the fitting assembly of FIG. 11 whenassembled.

FIG. 13 is a side view of one embodiment of a straight tube (withoutflanged ends) including a fitting assembly at each end in accordancewith one aspect of the present invention.

FIG. 14 is a cross-sectional side view of one end of the tube andfitting assembly of FIG. 13.

DETAILED DESCRIPTION

In FIG. 1, a block diagram of the essential elements of a conventionalliquid chromatography (LC) system is provided. A reservoir 101 containsa solvent or mobile phase 102. Tubing 103 connects the mobile phase 102in the reservoir 101 to a pump 105. The pump 105 is connected to asample injection valve 110 which, in turn, is connected via tubing to afirst end of a guard column (not shown). The second end of the guardcolumn (not shown) is in turn connected to the first end of a primarycolumn 115. The second end of the primary column 115 is then connectedvia tubing to a detector 117. After passing through the detector 117,the mobile phase 102 and the sample injected via injection valve 110 areexpended into a second reservoir 118, which contains the chemical waste119. As noted above, the sample injection valve 110 is used to inject asample of a material to be studied into the LC system. The mobile phase102 flows through the tubing 103 which is used to connect the variouselements of the LC system together.

When the sample is injected via sample injection valve 110 in the LCsystem, the sample is carried by the mobile phase through the tubinginto the column 115. As is well known in the art, the column 115contains a packing material which acts to separate the constituentelements of the sample. After exiting the column 115, the sample (asseparated via the column 115) then is carried to and enters a detector117, which detects the presence or absence of various chemicals. Theinformation obtained by the detector 117 can then be stored and used byan operator of the LC system to determine the constituent elements ofthe sample injected into the LC system. Those skilled in the art willappreciate that FIG. 1 and the foregoing discussion provide only a briefoverview of a simplistic LC system that is conventional and well knownin the art, as is shown and described in U.S. Pat. No. 5,472,598, issuedDec. 5, 1995 to Schick, which is hereby incorporated by reference as iffully set forth herein. Those skilled in the art will also appreciatethat while the discussion herein focuses on a LC system, otheranalytical systems can be used in connection with various embodiments ofthe invention, such as a mass spectrometry, microflow chromatography,nanoflow chromatography, nano-scale liquid chromatography, capillaryelectrophoresis, or reverse-phase gradient chromatography system.

Preferably, for an LC system to be biocompatible, the various components(except where otherwise noted) that may come into contact with theeffluent or sample to be analyzed are made of the synthetic polymerpolyetheretherketone, which is commercially available under thetrademark “PEEK” from Victrex. The polymer PEEK has the advantage ofproviding a high degree of chemical inertness and thereforebiocompatibility; it is chemically inert to most of the common solventsused in LC applications, such as acetone, acetonitrile, and methanol (toname a few). PEEK also can be machined by standard machining techniquesto provide smooth surfaces. Those skilled in the art will appreciatethat other polymers may be desirable in certain applications.

Referring now to FIG. 2, a first embodiment of a tube 1 is shown. Asshown in FIG. 2, the tube 1 includes a flanged first end 2 and a flangedsecond end 3.

FIG. 3 shows a cross-section of one embodiment of a flanged first end 2of the tube 1 as shown in FIG. 2. It can be seen that the flanged firstend 2 of the tube 1 as shown has three distinct portions. These includean outer layer 4, an inner layer 5, and a passageway 6 defined by theinner layer 5. The inner layer 5 generally comprises a biocompatiblematerial. The inner diameter of the inner layer 5 can be a variety ofsizes, including, but not limited to 10 μm, 15 μm, 20 μm, 25 μm, 30 μm,35 μm, 40 μm, 45 μm, 50 μm, 75 μm, 100 μm, 125 μm, 150 μm, 175 μm, 200μm, 250 μm, or 500 μm, or so.

FIG. 4 shows a cross-section of one embodiment of a flared first end 2′of the tube 1. It can be seen that the flared first end 2′ of the tube 1as shown also has three distinct portions. These include all outer layer4′, an inner layer 5′, and a passageway 6′ defined by the inner layer5′. Once again, the inner layer 5′ generally comprises a biocompatiblematerial. The inner diameter of the inner layer 5′ can be a variety ofsizes, including, but not limited to 10 μm, 15 μm, 20 μm, 25 μm, 30 μm,35 μm, 40 μm, 45 μm, 50 μm, 75 μm, 100 μm, 125 μm, 150 μm, 175 μm, 200μm, 250 μm, or 500 μm, or so.

FIG. 5 shows a cross-section of one embodiment of an angled first end 2″of the tube 1. It can once again be seen that the angled first end 2″ ofthe tube 1 as shown has three distinct portions. These include an outerlayer 4″, an inner layer 5″, and a passageway 6″ defined by the innerlayer 5″. Once again, the inner layer 5″ generally comprises abiocompatible material. The inner diameter of the inner layer 5″ can bea variety of sizes, including, but not limited to 10 μm, 15 μm, 20 μm,25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 75 μm, 100 μm, 125 μm, 150 μm,175 μm, 200 μm, 250 μm, or 500 μm, or so.

It will be appreciated that the tube 1 can comprise a number ofdifferent materials depending on the particular application, as that mayinvolve a particular type of sample, a particular type of solvent,and/or a particular pressure range. For example, the outer layer 4 (or4′ or 4″) of tube 1 can comprise a metal, such as stainless steel (suchas 316 stainless steel) or titanium, or a reinforced polymeric material,including composite or braided materials, such as polymeric materialsthat are reinforced or braided with carbon, carbon fibers, steel fibers,or the like. In embodiments comprising a metallic outer layer 4 (or 4′or 4″), the metal temper can be varied to provide a balance between highpressure capability and tubing flexibility. The inner layer 5 (or 5′ or5″) can comprise a biocompatible polymer, such as polyetheretherketone(PEEK). Other polymer materials which may be used for the inner layer 5(or 5′ or 5″) include, but are not limited to, TEFLON®, TEFZEL®,DELRIN®, perfluoroalkoxy (PFA, also called perfluoroalkoxyethylene),fluorinated ethylene propylene (PEP), polytetrafluoroethylene (PETE),ETFE (a polymer of tetrafluoroethylene and ethylene), polyetherimide(PEI), polyphenylene sulfide (PPS), polypropylene, sulfone polymers,polyolefins, polyimides, other polyaryletherketones, otherfluoropolymers, polyoxymethylene (POM), and others, depending on theforegoing factors or perhaps others. In addition, PEEK (or otherpolymers) may be used that is reinforced or braided with carbon, carbonfibers, steel fibers, or the like. Furthermore, in certain embodimentsthe inner layer 5 (or 5′ or 5″) may be coated with a material toincrease strength, improve chemical resistance, improve temperaturestability, or reduce permeability. Such coatings include, but are notlimited to, metallization, polymeric coating, silicon-based coatings,and carbon-based coatings. Additionally, in certain embodiments theinner layer may be heat treated to improve properties such ascrystallinity, chemical resistance, or permeability. The final tube 1may be treated to further improve the performance, including heattreatment or annealing to strengthen the polymer components, orpressurizing, with or without added heat, to allow the inner layer toconform to the outer layer. A mandrel can be used in the inner diameterof the inner layer to preserve the passageway.

Those skilled in the art will further appreciate that tube 1 as shown inFIG. 2 can comprise one or more fitting connection (not shown) forconnecting tube 1 to another component in an LC, or other AI system (notshown), and that the other component may be any one of wide variety ofcomponents. Such components include pumps, columns, filters, guardcolumns, injection valves and other valves, detectors, pressureregulators, reservoirs, and other fittings, such as unions, tees,crosses, adapters, splitters, sample loops, connectors, and the like.

FIG. 6 shows an embodiment of one end of a flanged, flared or angledtube 1, as shown in FIG. 2, with an assembled fitting assembly 50 at theend of the tube 1. As detailed above, tube 1 comprises first end 2 andsecond end (not shown). Visible in the assembled fitting assembly 50 arefirst end 51, second end 53, nut head 52, first non-threaded portion 55,externally threaded portion 54, tapered portion 56, and secondnon-threaded portion 57. The passageway (not visible) is adapted toallow tube 1 to extend through the fitting assembly 50.

FIG. 7 shows a cross-section of the embodiment of one end of a flanged,flared or angled tube and assembled fitting assembly as shown in FIG. 6.It can be seen that the flanged first end 2 of the tube 1 as shown hasthree distinct portions. These include an outer layer 4, an inner layer5, and a passageway 6 defined by the inner layer 5. The inner layer 5generally comprises a biocompatible material. The inner diameter of theinner layer 5 can be a variety of sizes, including, but not limited to10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 75 μm,100 μm, 125 μm, 150 μm, 175 μm, 200 μm, 250 μm, or 500 μm, or so. It canalso be seen in FIG. 7 that fitting assembly 50 comprises first end 51,second end 53, nut head 52, first non-threaded portion 55, externallythreaded portion 54, tapered portion 56, and second non-threaded portion57. The passageway 58 (mostly obscured by tube 1) is adapted to allowtube 1 to extend through the fitting assembly 50.

Referring now to FIG. 8, an alternative embodiment of a tube 1000 isillustrated. Like the tube 1 of FIG. 2, the tube 1000 of FIG. 8 includesa first end 1001 and a second end 1002, but the first end 1001 andsecond end 1002 of tube 1000 are essentially straight instead offlanged, flared or angled. This allows any standard fitting assembly tobe used with tube 1000.

In addition, tube 1000 includes a first tip assembly 1003 and a secondtip assembly 1004. Those skilled in the art will appreciate that anyfitting that can be used with an LC or other analytical instrument (AI)system can be used in conjunction with the tube 1000.

FIG. 9 shows a cross-section of one embodiment of the first end 1001 andfirst tip assembly 1003 of the tube 1000 shown in FIG. 8. Tube 1000again comprises three distinct portions, the outer layer 1005, the innerlayer 1006, and a passageway 1007 defined by the inner layer 1006. Thefirst tip assembly 1003 also comprises three distinct portions, anextension of the inner layer 1006′ that protrudes from outer layer 1005,an extension of the passageway 1007′ defined by the extension of theinner layer 1006′, and a tip 1008 overmolded onto the extension of theinner layer 1006′ and extension of the passageway 1007′ that protrudesfrom outer layer 1005. One method of making tube 1000 is by extruding aprecision polymer tube, and inserting it into a stainless steel tube.Coextruded polymer tubes can also be employed to tailor the materialproperties to the application. The ends of the polymer tube can beinsert molded onto the tubing to provide an inert wetted face. Forexample, a PEEK liner tube can be used with a stainless steel tubeincluding a carbon fiber reinforced tip. The tip to liner tube adhesionresulting from PEEK to PEEK insert molded bond prevents any liquidflowing between the layers. Carbon fiber tips can give the tubing addedstrength to resist damage from the fluid pressure and any compressionfrom a fitting assembly.

Once again, it will be appreciated that the tube 1000 can comprise anumber of different materials, depending on the particular application,as that may involve a particular type of sample, a particular type ofsolvent, and/or a particular pressure range. For example, the outerlayer 1005 of tube 1000 can comprise a metal, such as stainless steel(such as 316 stainless steel) or titanium, while the inner layer 1006can comprise a biocompatible polymer, such as polyetheretherketone(PEEK), fused silica, or coated fused silica, such as PEEK-coated fusedsilica. Other polymer materials which may be used for the inner layer1006 include, but are not limited to, TEFLON®, TEFZEL®, DELRIN®,perfluoroalkoxy (PEA, also called perfluoroalkoxyethylene), fluorinatedethylene propylene (FEP), polytetrafluoroethylene (PETE), ETFE (apolymer of tetrafluoroethylene and ethylene), polyetherimide (PEI),polyphenylene sulfide (PPS), polypropylene, sulfone polymers,polyolefins, polyimides, other polyaryletherketones, otherfluoropolymers, polyoxymethylene (POM), and others, depending on theforegoing factors or perhaps others. In addition, PEEK (or otherpolymers) may be used that is reinforced or braided with carbon, carbonfibers, glass fibers, steel fibers, or the like. In addition, steeltubes comprising unfilled PEEK tips can be used with unfilled PEEK linertubing, and fluoropolymers (for example ethylene tetrafluoroethylene(TTE), fluorinated ethylene propylene (FEP), perfluoroalkoxy (PEA),polytetrafluoroethylene (PETE), polyvinylidenefluoride (PVDF) ormodified fluoroalkoxy (MFA)) can be used in the tips and/or liner tubes.In addition, fluoropolymer tubing and tips and be used with a polymer(for example natural or braided PEEK) jacket for a totally non-metallicversion of tube 1000.

Furthermore, in certain embodiments the inner layer 1006 may be coatedwith a material to increase strength, improve chemical resistance,improve temperature stability, or reduce permeability. Such coatingsinclude, but are not limited to, metallization, polymeric coating,silicon-based coatings, and carbon-based coatings. Additionally, incertain embodiments the inner layer may be heat treated to improveproperties such as crystallinity, chemical resistance, or permeability.The final tube 1000 may be treated to further improve the performance,including heat treatment or annealing to strengthen the polymercomponents, or pressurizing, with or without added heat, to allow theinner layer to conform to the outer layer. A mandrel can be used in theinner diameter of the inner layer to preserve the passageway.Furthermore, the outer layer 1005 can be crimped to prevent or reducethe inner layer 1006 from sliding within the outer layer 1005.

FIG. 10 shows a cross-section of an alternative embodiment of the firstend 1001′ and first tip assembly 1003′ of the tube 1000 shown in FIG. 8.Tube 1000 again comprises three distinct portions, the outer layer 1005,the inner layer 1006, and a passageway 1007 defined by the inner layer1006. However, this embodiment of tube 1000 comprises a retentionfeature, which in this embodiment is a barb 1009, machined onto the endof the outer layer 1005, the inner layer 1006 protrudes from the barb1009 of the outer layer 1005, and the barb 1009 and protruding portion1006′ of inner layer 1006 are overmolded together with tip 1008. Onemethod of making tube 1000 is by extruding a precision polymer innerlayer 1006, and inserting it into a stainless steel outer layer 1005that comprises a barb 1009 at each end. Coextruded polymer tubes canalso be employed to tailor the material properties to the application.Additionally, the surface of the inner layer 1006 can be modified toimprove the bonding to the tip 1008, for example by surface roughening,plasma treatment, corona discharge, or other comparable method. The endsof the inner layer 1006′ protrude beyond the outer layer 1005 to preventor reduce occlusion of the inner diameter and allow the inner layer tobe externally fixed so that it is well-centered within the tip duringinsert injection molding. The tip 1008 of the tube 1000 are insertinjection molded onto the barb 1009 and protruding portion of innerlayer 1006′ and then trimmed to provide a one-piece construction with anall-polymer inert wetted face. Alternatively, the tip 1008 may becomprised of cut pieces of tubing that are welded over the barb 1009 andprotruding portion of inner layer 1006′ by RF welding or other bondingtechnique. While the embodiment of the tube 1000 in FIG. 10 includes abarb 1009 as the retention feature at the end of outer layer 1005, othergeometries can be used as retention features to achieve similar results,such as undercuts, ribs, grooves, threads, one or more cross-drilledhole, one or more dimple, a reverse taper, a flange, a geometric shape,including, but not limited to, a triangle, a square, a rectangle, apentagon, a hexagon, a heptagon, or an octagon, or surface rougheningwithout a retention feature.

Referring now to FIG. 11, an embodiment of a fitting assembly 100 isshown. As shown in FIG. 11, the fitting assembly 100 includes a nut 110,a ferrule 20, and a ferrule tip 30. The first end 111 of the nut 110includes a non-threaded portion 118 near the first end 111, and the nuthead 112. The other or second end 113 of the nut 110 includes anexternally threaded portion 114. Passageway 115 through nut 110 is alsoshown as is lip 119. As detailed below, passageway 115 and lip 119 areadapted to receive and securely hold a combination of the ferrule 20 anda first end of the ferrule tip 30. As shown in FIG. 11, each of nut 110,ferrule 20, and ferrule 30 are generally circular and symmetric about acenter axis. Those skilled in the art will realize that a circular shapehas advantages, but the outer diameters in particular of nut head 112may have a non-circular shape if desired, such as having flat or concavesurface portions, to allow an operator to more easily grip and rotatenut 110. As detailed herein, the externally threaded portion 114 of thenut 110 is adapted to be removably secured to a corresponding threadedportion of a port, a fitting, or a component of an LC or otheranalytical instrument (AI) system (not shown). Those skilled in the artwill appreciate that the externally threaded portion 114 of the nut 110may be adapted so that it can be removably engaged with any sized port,fitting, or component of an LC or other AI system (not shown). The useof external threads on one element, such as the nut 110, versus internalthreads, is a matter of selection. Those skilled in the art willtherefore appreciate that the nut 110 in an alternative embodiment couldhave internal threads (not shown) located near a second end, which couldbe engaged with external threads (not shown) located near the first endof an alternative embodiment of a port, fitting, or component of an LCor AI system (not shown).

Still referring to FIG. 11, it can be seen that the ferrule 20 as shownhas three distinct portions. These include a first end 21, a middleportion 22, and a second end 23. First end 21 has a tapered portion 24of the outer diameter so that the tapered portion 24 forms a truncatedconical shape. As shown in FIG. 11, the tapered portion 24 of the firstend 21 defines an angle from the axis of the ferrule 20. However, thoseskilled in the art will appreciate that the tapered portion 24 candefine a different angle if desired. As detailed below, the taperedportion 24 of the first end 21 is adapted to be removably received in aninternally tapered portion of passageway 115 of nut 110. Also shown isthis embodiment of ferrule 20 are fingers or members 25, which define aslot 26 through the tapered portion 24 of the first end 21 and themiddle portion 22 of the ferrule 20. Although only two fingers ormembers 25 are visible in FIG. 11, ferrule 20 can comprise a pluralityof fingers or members, which in turn define a plurality of slots, whichcan extend any distance through the ferrule 20 from the first endportion 21 up to but not including the second end 23 of the ferrule 20.Passageway 27 through ferrule 20 is also shown.

Still referring to FIG. 11, it can be seen that the ferrule tip 30 asshown also has three distinct portions. Ferrule tip 30 includes a firstend 31, a middle portion 32, and a second end 33. In this embodiment thefirst end 31 and second end 33 include first and second tapered portions34 and 35, respectively, on the outer diameter of the ferrule tip 30that are shaped as a truncated cone. First and second tapered portions34 and 35 extend above the middle portion 32 of the ferrule tip 30,thereby forming first and second lips 36 and 37, respectively. Asdetailed below, the first end 31 of the ferrule tip 30 is adapted toabut the second end of ferrule 20 within the passageway 115 of the nut110, and first lip 36 is adapted to be removably received in thepassageway 115 of the nut 110. Passageway 38 through ferrule tip 30 isalso shown. In general, we believe that the externally threaded portion114 of the nut 110 and shape and size of the second tapered portion 35of the ferrule tip 30 should be of a shape and size so that assembledfitting assembly 100 may be easily secured to a port, fitting, orcomponent of a LC or AI system (not shown) and may also be easilyremoved there from, in either case by rotating the nut head 112 (andthereby fitting assembly 100) relative to the port, fitting, orcomponent.

Generally, the rotational force or torque applied to connect to the nut110, ferrule 20, ferrule tip 30 and tubing extending therethrough (notshown) to a port, fitting, or component in an LC or AI systemaccomplishes two major tasks. First, the force of the connection of thefitting assembly 100 needs to be sufficient to provide a scaled and leakproof connection to the port, fitting, or component. In addition, theforce of the connection of the fitting assembly 100 needs to besufficient so that the tubing is securely held and is sufficient toprevent detachment due to the hydraulic force of the fluid movingthrough the tubing. We believe that the latter function typicallyinvolves greater forces than the former. We believe that the fittingassembly 100 (such as shown in FIG. 11) provides an advantage in that itallows for better connections at higher pressures without requiringhigher forces to connect fitting assembly 100.

FIG. 12 shows the embodiment of the fitting assembly 100 shown in FIG.11 upon assembly by an operator. Like features and elements in thedrawings have the same numerals in the various figures. Upon assembly offitting assembly 100 only nut 110 and ferrule tip 30 are visible, asferrule 20 (not visible) is positioned within the passageway 115 (notvisible) of nut 110. Additionally, it can be seen that the first taperedportion 34 and first lip 36 of the first end 31 of the ferrule tip 30are also not visible, as these elements are also positioned within thepassageway 115 (not visible) of nut 110. Still visible upon assembly ofthe fitting assembly 100 are first end 111, second end 113, nut head112, non-threaded portion 118, and externally threaded portion 114 ofthe nut 110, and middle portion 32, second end 33, second taperedportion 35, and second lip 37 of the ferrule tip 30. The passageways115, 27, and 38 of the nut 110, ferrule 20, and ferrule tip 30 (notvisible) are adapted to allow tubing (not shown) to extend through eachof nut 110, ferrule 20, and fitting 30, and thus through the fittingassembly 100.

FIG. 13 shows an embodiment of a straight tube 1000, as shown in FIG. 8,with an assembled fitting assembly 100 as shown in FIG. 12 at each endof the tube 1000. As detailed above, tube 1000 comprises first end 1001and second end 1002, and first tip assembly 1003 and second tip assembly1004. Visible in each of the assembled fitting assemblies 100 are firstend 111, second end 113, nut head 112, non-threaded portion 118, andexternally threaded portion 114 of the nut 110, and middle portion 32,second end 33, second tapered portion 33, and second lip 37 of theferrule tip 30. The passageways 115, 27, and 38 of the nut 110, ferrule20, and ferrule tip 30 (not visible) are adapted to allow tube 1000 toextend through each of nut 110, ferrule 20, and fitting 30, and thusthrough the fitting assembly 100.

Additional details of the cross-section of the tube 1000 as shown inFIG. 8, the fitting assembly 100 as shown in FIG. 12, including theembodiment of the tip assembly as depicted in FIG. 10, are shown in FIG.14. Nut 110 has a first end 111, a nut head 112, an unthreaded portion118, a second end 113, and an externally threaded portion 114.Passageway 115 (largely excluded from view by tube 1000) extends throughnut 110 and includes an internally tapered portion 116. The internallytapered portion 116 of the nut 110 is adapted to receive and securelyhold the tapered portion 24 of the first end portion 21 of the ferrule20 when the fitting assembly 100 is assembled. As shown in FIG. 14, theexternally threaded portion 114 forms a lip 119 near the second end 113of the nut 110. The externally threaded portion 114 of the nut 110 isadapted to be removably secured to a corresponding threaded portion of aport, a fitting, or a component of an LC or other analytical instrument(AI) system (not shown).

Additional details of the cross-section of the ferrule 20 are also shownin FIG. 14. The ferrule 20 has a first end 21 with an externally taperedportion 24, a middle portion 22 which in this embodiment, as shown inFIG. 14, is not tapered, and a second end 23. Although not shown, itwill be appreciated that the angle of the tapered portion 24 from theaxis of ferrule 20 may differ from the angle defined by the internallytapered portion 116 of the nut 110. For example, the angle defined bythe tapered portion 24 of the ferrule 20 may be greater than the angledefined by the internally tapered portion 116 of the nut 110, to make iteasier to obtain sufficient tubing retention with fitting assembly 100when nut 110, ferrule 20, and ferrule tip 30 are engaged and assembled.As detailed above, the tapered portion 24 of the first end 21 of ferrule20 is adapted to be removably received in the internally tapered portion116 of passageway 115 of nut 110. Not shown in FIG. 14 are slots 26extending through the tapered portion 24 of the first end 21 and themiddle portion 22 of the ferrule 20. It will be appreciated by theskilled artisan that the slots 26 can extend any distance through theferrule 20 from the first end portion 21 up to but not including thesecond end portion 23 of the ferrule 20. As shown in FIG. 12, thepassageway 27 (not visible because occupied by tube 1000) throughferrule 20 is not tapered.

Additional details of the cross-section of the ferrule tip 30 are alsoshown in FIG. 14. The ferrule tip 30 has a first end 31, a middleportion 32, and a second end 33, and further has an externally taperedportion 34 at the first end 31 and an externally tapered portion 35 atthe second end portion 33 of the ferrule lip 30. As shown in FIG. 14,the externally tapered portions 34 and 35 extend further from thecentral axis of the ferrule tip 30 than the middle portion 32, therebydefining a first lip 36 and a second lip 37, respectively, and theexternally tapered portion 34 at the first end 31 of the ferrule tip 30is tapered in the opposite direction compared to the externally taperedportion 35 at the second end 33 of the ferrule tip 30. The first end 31of the ferrule 30 is adapted to abut the second end 23 of the ferrule 20when the fitting assembly 100 is assembled. In addition, the first lip36 is adapted to be securely retained by lip 119 in passageway 115 ofthe nut 110 when the fitting assembly 100 is assembled. Also shown inFIG. 14 is passageway 38 (not visible because occupied by tube 1000)extending through the ferrule tip 30.

FIG. 14 also shows a cross-section of an alternative embodiment of thefirst end 1001′ and first tip assembly 1003′ of the tube 1000 shown inFIG. 10. Tube 1000 again comprises three distinct portions, the outerlayer 1005, the inner layer 1006, and a passageway 1007 defined by theinner layer 1006. However, this embodiment of tube 1000 comprises a barb1009 machined onto the end of the outer layer 1005, a portion of theinner layer 1006′ protrudes from the barb 1009 of the outer layer 1005,and the barb 1009 and protruding portion 1006′ of inner layer 1006 areovermolded together with tip 1008.

Generally, the rotational force or torque applied to connect to thefitting assembly 100 and tube 1000 extending therethrough to a port,fitting, or component in an LC or AI system accomplishes two majortasks. First, the force of the connection of the fitting assembly 100needs to be sufficient to provide a sealed and leak proof connection tothe port, fitting, or component. In addition, the force of theconnection of the fitting assembly 100 needs to be sufficient so thatthe tube 1000 is securely held and is sufficient to prevent detachmentdue to the hydraulic force of the fluid moving through the tube 1000.

It will be appreciated that the nut 110, ferrule 20, and ferrule tip 30can comprise a number of different materials. For example, each of nut110, ferrule 20 and ferrule tip 30 in a fitting assembly 100 cancomprise a metal, such as stainless steel, or each can comprise adifferent material, such as a polymer. For example, the fitting assembly100 can comprise a nut 110 comprising polyetheretherketone (PEEK), aferrule 20 comprising stainless steel, and a ferrule tip 30 comprisingPEEK. It will be appreciated that a variety of metals and polymers maybe selected for any one or more of nut 110, ferrule 20, and ferrule tip30 depending on the particular application, as that may involve aparticular type of sample, a particular type of solvent, and/or aparticular pressure range. In addition, the selection of materials forthe tubing may lead to a selection of a particular material for nut 110,ferrule 20, and/or ferrule tip 30. In addition. PEEK (or other polymers)may be used that is reinforced with carbon, carbon fibers or steelfibers, or the like. Other polymer materials which may be used include,but are not limited to, TEFLON®, TEFZEL®, DELRIN®, polyphenylene sulfide(PPS), polypropylene, and others, depending on the foregoing factors orperhaps others. Those skilled in the art will further appreciate thatfitting assembly 100 is shown as a fitting connection for connectingtubing to another component in an LC or other AI system, and that theother component may be any one of wide variety of components. Suchcomponents include pumps, columns, filters, guard columns, injectionvalves and other valves, detectors, pressure regulators, reservoirs, andother fittings, such as unions, tees, crosses, adapters, splitters,sample loops, connectors, and the like.

In order for a fitting assembly to seal, it should generally remain incompression (relative to the conical surface of the port) throughout allenvironmental conditions. Therefore, in certain aspects a coating with ahigh coefficient of friction between the outer surface of the tubematerial is applied to at least a portion of the internal bore surfaceof the described fitting assembly 100. The high coefficient of frictionbetween the outer surface of the tube and the internal bore surface ofthe fitting connection or assembly 100 keeps the tube from extruding outof the port during pressurization, which results in dramaticallyincreased burst pressure. In such embodiments the fitting connection orassembly is coated at the internal bore surface that contacts the tubestarting at approximately 0.005 inches, about 0.0075 inches, about 0.01inches, or about 0.02 inches from the tip. Coatings suitable for usewith the presently described fitting connection or assembly include, butare not limited to, nickel, silica carbide, copper, and diamondcoatings, and combinations thereof.

Methods of using the fitting assembly 100 (such as shown in FIG. 11 andFIG. 12) are now described in further detail. An operator can firstprovide a nut 110, ferrule 20 and ferrule tip 30, as well as tube 1000(shown in FIG. 13 and FIG. 14). In one approach, the operator can inserta portion of the tube 1000 through the passageways 115, 27, and 38 ofnut 110, ferrule 20 and ferrule tip 30, respectively, in that orderwithout assembling or otherwise connecting any of nut 110, ferrule 20and ferrule tip 30. Next, the operator can insert the ferrule 20 intothe passageway 115 in the second end 113 of the nut 110, and the insertthe first end 31 of the ferrule tip 30 into the passageway 115 in thenut 110, such that the first end 31 of the ferrule tip 30 abuts thesecond end 23 of the ferrule 20 and pushes the first end 21 of theferrule 20 against the internal tapered portion 116 of the passageway115 of the nut 110, and the first lip 34 of the ferrule tip 30 isretained within the passageway 115 of the nut 110 by lip 119. Theoperator can then engage the externally threaded portion 114 of the nut110 with the internally threaded portion of a port, fitting, orcomponent of a LC or AI system (not shown). Once the externally threadedportion 114 of the nut 110 and the internally threaded portion of theport, fitting, or component of a or AI system begin to mate or engage,the operator then rotates the nut head 112 of the fitting assembly 100relative to the port, fitting, or component of a LC or AI system,rotates the port, fitting, or component of a LC or AI system relative tothe nut head 112 of the fitting assembly 100, or rotates both the nuthead 112 of the fitting assembly 100 and the port, fitting, or componentof a LC or AI system relative to each other. By so rotating the nut head112 of the fitting assembly 100 and the port, fitting, or component of aLC or AI system relative to one another, the operator drives the ferrule20 and ferrule tip 30 further into the interior passageway 115 of thenut 110. In doing so, the operator thus forces the first end 21 of theferrule 20 against the internally tapered portion 116 of the passageway115 of nut 110 and also forces the externally tapered portion 34 of thefirst end of ferrule tip 30 into the passageway 115 of the nut 110, thusengaging the first lip 36 of the ferrule tip 30 with the lip 119 of thepassageway 115 of the nut 110. In doing so, the externally tapered firstend 24 of the ferrule 20 is compressed and held firmly against theinternally tapered portion 116 of the passageway 115 of the nut 110,thereby forming a leak proof connection. Because the first ends 24 ofthe ferrule 20 may be deformed or compressed as it is forced against thetapered portion 116 of the passageway 115 of the nut 110, a leak proofconnection may be obtained by the operator without the use of additionaltools such as a wrench, pliers or the like. Alternatively, fittingassembly 100 can be provided to the operator pre-assembled. In onespecific embodiment, when tubing having an outer diameter of 0.0625inches is used, the minimum diameter of the passageway in the fittingassembly can range between about 0.065 and about 0.067 inches.

To disconnect a fitting assembly 100, such as shown in FIG. 11 and FIG.12, an operator may either rotate the fitting assembly 100 relative tothe port, fitting, or component of a LC or AI system (not shown), rotatethe port, fitting, or component of a LC or AI system relative to thefitting assembly 100, or rotate both the port, fitting, or component ofa LC or AI system and the fitting assembly 100 relative to each other.By rotating the port, fitting, or component of a LC or AI system and/orthe fitting assembly 100 relative to one another, the operator thusrotates the externally threaded portion 114 of nut 110 and theinternally threaded portion of the port, fitting, or component of a LCor AI system, respectively, and thereby disengages the connectionbetween such threaded portions. At this point, the operator can use theassembly 100 and the leak proof connection it provides, until theoperator decides to remove the tube 1000 (shown in FIG. 13 and FIG. 14)from the assembly 100. By selecting the direction of the threading ofthe externally threaded portion 114 of the nut 110 and internallythreaded portion of the port, fitting, or component of a LC or AIsystem, respectively, the operator can turn the entire fitting assembly100 (when connected) by turning or rotating nut 110, such that thefitting assembly 100 rotates relative to the port, fitting, or componentof a LC or AI system (not shown) and disengages therefrom. Thus, theentire fitting assembly 100 is easily disconnected from the port,fitting, or component of a LC or AI system (not shown).

The following example is included to demonstrate preferred embodimentsof the invention. It should be appreciated by those of skill in the artthat the techniques disclosed in the example which follows representtechniques discovered by the inventors to function well in the practiceof the invention, and thus can be considered to constitute preferredmodes for its practice. However, those of skill in the art should, inlight of the present disclosure, appreciate that many changes can bemade in the specific embodiments which are disclosed and still obtain alike or similar result without departing from the spirit and scope ofthe invention. The present invention is not to be limited in scope bythe specific embodiments described herein, which are intended as singleillustrations of individual aspects of the invention, and functionallyequivalent methods and components are within the scope of the invention.Indeed, various modifications of the invention, in addition to thoseshown and described herein, will become apparent to those skilled in theart from the foregoing description. Such modifications are intended tofall within the scope of the appended claims.

Performance of a flanged tube 1 as described herein, for example asshown in FIG. 2, and straight tube 1000 as described herein, for exampleas shown in FIG. 6, were tested as detailed below. In a first test, itwas determined that flanged tube 1 held to over 30,000 psi at about 4.0inch-pounds of torque, prior to failure of the tube. In the second test,it was determined that straight tube 1000 held to about 30,000 psi atabout 10.0 inch-pounds of torque, prior to failure of the fittingsystem. The design is such that a fitting can apply direct pressure tothe flange face seal, allowing a high pressure seal with low actuationtorque.

While the present invention has been shown and described in variousembodiments, those skilled in the art will appreciate from the drawingsand the foregoing discussion that various changes, modifications, andvariations may be made without departing front the spirit and scope ofthe invention as set forth in the claims. Hence the embodiments shownand described in the drawings and the above discussion are merelyillustrative and do not limit the scope of the invention as defined inthe claims herein. The embodiments and specific forms, materials, andthe like are merely illustrative and do not limit the scope of theinvention or the claims herein.

We claim:
 1. A tube for use in a liquid chromatography system, comprising: a) an outer layer having an inner surface and an outer surface, and having a first and a second end, wherein at least one of said first and second ends of said outer layer comprises a tip portion and a retention feature for retaining said tip portion, wherein said tip portion comprises a polymer and wherein said retention feature is a barb, an undercut, one or more cross-drilled hole, a reverse taper or a flange; and b) a biocompatible inner layer having an inner surface, an outer surface, a first end, a second end and a passageway therethrough, wherein said inner layer is located within said outer layer.
 2. The tube according to claim 1, wherein said first end of said outer layer comprises a first tip portion and a first retention feature, and said second end of said outer layer comprises a second tip portion and a second retention feature, wherein said first and second tip portions comprise a polymer.
 3. The tube according to claim 1, wherein said outer layer is comprised of metal.
 4. The tube according to claim 1, wherein said biocompatible inner layer comprises polyetheretherketone (PEEK).
 5. The tube according to claim 1, wherein at least a portion of said inner surface of said outer layer interacts with at least a portion of said outer surface of said inner layer.
 6. The tube according to claim 5, wherein said interaction is friction-based.
 7. The tube according to claim 1, wherein said tip portion comprises PEEK.
 8. The tube according to claim 1, further comprising at least a first fitting assembly.
 9. The tube according to claim 8, further comprising at least a first and a second fitting assembly.
 10. The tube according to claim 8, wherein said fitting assembly comprises: a) a nut having a first end and a second end, and having a passageway therethrough, wherein said passageway has an internally tapered portion and a lip proximal said second end of said nut, and wherein said second end of said nut has an externally threaded portion; b) a ferrule having a first externally tapered end and a second end and having a passageway therethrough, wherein said first externally tapered end of said ferrule is adapted to securely engage with said tapered portion of said passageway in said nut; and c) a ferrule tip having a first externally tapered end, a central portion, and a second externally tapered end, wherein said first externally tapered end and said central portion define a first lip and said second externally tapered end and said central portion define a second lip, and wherein said first end of said ferrule tip is adapted to abut with said second end of said ferrule within said passageway of said nut, and said first lip of said ferrule tip securely engages said lip of said nut.
 11. A tube assembly for use in a liquid chromatography system, comprising: a) a tube comprising: i) an outer layer having an inner surface and an outer surface, and having a first and a second end, wherein at least one of said first and second ends of said outer layer comprises a tip portion and a retention feature for retaining said tip portion, wherein said tip portion comprises a polymer and wherein said retention feature is a barb, an undercut, one or more cross-drilled hole, a reverse taper or a flange; and ii) a biocompatible inner layer having an inner surface, an outer surface, a first end, a second end and a passageway therethrough, wherein said inner layer is located within said outer layer; and b) at least a first fitting assembly associated with said first or second end of said outer layer.
 12. The tube assembly according to claim 11, wherein said first end of said outer layer comprises a first tip portion and a first retention feature, and said second end of said outer layer comprises a second tip portion and a second retention feature, wherein said first and second tip portions comprise a polymer.
 13. The tube assembly of claim 12, wherein said first retention feature is the same as said second retention feature.
 14. An analytical instrument system comprising at least one tube assembly comprising: a) a tube comprising: i) an outer layer having an inner surface and an outer surface, and having a first and a second end, wherein at least one of said first and second ends of said outer layer comprises a tip portion and a retention feature for retaining said tip portion, wherein said tip portion comprises a polymer and wherein said retention feature is a barb, an undercut, one or more cross-drilled hole, a reverse taper or a flange; and ii) a biocompatible inner layer having an inner surface, an outer surface, a first end, a second end and a passageway therethrough, wherein said inner layer is located within said outer layer; and b) at least a first fitting assembly associated with said first or second end of said outer layer, said fitting assembly comprising: i) a nut having a first end and a second end, and having a passageway therethrough, wherein said passageway has an internally tapered portion and a lip proximal said second end of said nut, and wherein said second end of said nut has an externally threaded portion; ii) a ferrule having a first externally tapered end and a second end and having a passageway therethrough, wherein said first externally tapered end of said ferrule is adapted to securely engage with said tapered portion of said passageway in said nut; and iii) a ferrule tip having a first externally tapered end, a central portion, and a second externally tapered end, wherein said first externally tapered end and said central portion define a first lip and said second externally tapered end and said central portion define a second lip, and wherein said first end of said ferrule tip is adapted to abut with said second end of said ferrule within said passageway of said nut, and said first lip of said ferrule tip securely engages said lip of said nut.
 15. The system according to claim 14, wherein said analytical instrument system comprises an ultra high pressure or ultra high performance liquid chromatography system. 